Feeding device for machine tools

ABSTRACT

A mechanical storage device is attached to a feeding device for machine tools, particularly for grinding machines of globoid worms. The device enables preselection of machining operations which are to be repeatedly performed and where the tool is supported to be returned after a working phase into a position corresponding to its original starting position. A pair of coupling disks on a shaft is used and which are provided with dogs, controlling by their angular displacement different phases of the machining operation.

United States Patent [191 Hajsman 1451 July 17, 1973 FEEDING DEVICE FOR MACHINE TOOLS [75] Inventor: Vaclav Hajsman, Plzen,

Czechoslovakia [73] Assignee: Skoda, norodnia podnik, Plzen,

. Czechoslovakia 22 Filedf Dec. 21, 1971 211 Appl. 110.: 210,360

30 Foreign Application Priority um Dec. 22, 1970 Czechoslovakia 8671/70 [52] US. Cl. .[51/33 W, 51/55, 51/95 GH, 51/287 [51] Int. Cl. 1324b 5/04 [58] Field of Search 5 1/95 GH, 95 R, 33 W, 51/33 R, 55, 287, 58

[56] I References Cited UNITEDSTATES PATENTS 11/1934 Gleason =1 al. 51/33 R x 2,424,271 7/1947 Galloway 5l/33 W 3,060,643 10/1962 Wildhaber... 51/95 GH X 3,641,708 2/1972 Strejc 51/33 R 3,152,422 10/1964 Loxham 5l/95 GH X Primary Examiner-Donald G. Kelly Assistant Examiner-Howard N Goldbcrg Attorney-Murray Schaffer [5 7] ABSTRACT A mechanical storage device is attached to a feeding device for machine tools, particularly for grinding machines of globoid worms. The device enables preselection of machining operations which are to be repeatedly performed and where the tool is supported to be returned after a working phase into a position corresponding to its original starting position A pair of coupling disks on a shaft is used and which are provided with dogs, controlling by their angular displacement different phases of the machining operation.

4 Claims, 13 Drawing Figures PATENTED JUL 1 71975 SHEH 2 0f INVENTOR VHQLHV fig Sr mN BY A TORNE FEEDING DEVICE FOR MACHINE TOOLS BACKGROUND OF THE INVENTION This invention relates to an arrangement for the mechanical control of the means for feeding a tool towards a workpiece for a required distance and particularly for means to control the required cutting depth of a worm grinding machine.

The feeding device according to this invention can be applied to machine tools where the preselection of the feed may be for a certain time constant, which however can be continuously altered by changing another value depending on the working parameters, for instance on the axial distance when working globoid gears (worm and worm wheel) or by charging the apex angle when grinding conical surfaces or the like.

Known feed devices apply only a direct coupling between the preselected feeding distance and the real feeding value, that means the actual feeding value cannot be altered in a continuous manner by changes of another value which depends on some other parameter.

A drawback of the prior arrangement is the need of a manual intervention into the preselection of the feeding values in the event changes are desired of the fundamental parameters, as for instance in a grinding machine of globoid worms, if the axial distance is changed. In addition these prior arrangements do not enable a return movement which is necessary for automatically operating machines to obtain a repeating working cycle.

SUMMARY OF THE INVENTION It is an object of this invention to provide a feeding device for machine tools, particularly for grinding machines of globoid worms, which would operate automatically according to preselected conditions, insuring a correct working particularly of multithread worms.

According to the present invention a feeding device is provided having a mechanical storage attached to a driving means for the tool and workpiece respectively. The mechanical storage device comprises a reversible regulating driving means, driving a coupling shaft. The shaft supports a rotatably arranged coupling parts for both directions of movement, said coupling parts having dogs urged by spring means against a stationary stop provided with limit switches, controlling individual phases of the machining operation, said coupling parts adapted to be coupled both individually and together with said coupling shaft.

The feeding device according to this invention can be advantageously applied particularly for working of tooth flanks of single and multithreaded globoid worms. Another advantage of this invention is that it can be utilized when working multithreaded globoid worms, to obtain the preselection of the overall feeding distance, that is the overall required depth of removal of material and to obtain after reaching this distance (working of one thread of the globoid worm), a return movement of the tool into its starting position while maintaining the originally preselected feeding distance. When returning the tool into its starting position, the tool is automatically removed from the work surface.

The invention can be applied to all machines working in an automatic cycle, where the feeding distance depends on two parameters as is the case for a grinding machine of globoid worms on where it is necessary to maintain in a repeated cycle the starting position of the tool and the workpiece.

DESCRIPTION OF DRAWINGS In the accompanying drawings:

FIG. 1 is a perspective view of a grinding machine for grinding of tooth flanks of globoid worms,

FIG. 2 is a schematic view of interconnection of different elements of this grinding machine,

FIG. 3 is a schematic view of parts of the feeding device according to this invention,

FIG. 4 is a perspective view of a coupling unit as used in this feeding device,

FIG. 5 is a schematic diagram of control elements of a reversible regulating motor used for driving parts of the feeding device,

FIG. 6 to 11 are diagrams showing different position of parts of the coupling unit used in the feeding device,

FIG. 12 shows a globoid worm partly in a sectional view indicating positions of the grinding disk at the start and at the end of working,

FIG. 13 shows a schematic view of two globoid worms with different axial distances of the corresponding worm wheel and the different angular displacement of the grinding wheel for obtaining the same depth of material.

DESCRIPTION OF PREFERRED EMBODIMENT The grinding machine for grinding tooth flanks of globoid worms shown in FIG. 1 and 2 employs a conical grinding disk 15 to which a rotating motion is transmitted from a conventional driving means. A rotating motion is simultaneously transmitted to the globoid worm 9 which is to be worked and to a rotatable table 14 supporting the grinding disk 15. As seen in FIG. 2, the disk 15 is mounted on a shaft 17. The annular movement of the rotatable table 14 is limited in one direction by a first stop 10 which actuates a first limit switch l2, and in the other direction by a second stop 11 which actuates a second limit switch 13. The switches 12 and 1 3 are connected to feeding device 16 controlling gear transmissions 2 and 7. This limitation of the angular movement of the rotatable table 14 eliminates time losses which might occur due to its idle movement from the moment the grinding disk 15 comes out of engagement with the worked globoid worm 9 up to the moment of a new engagement. In addition to this rotating movement the rotating table 14 can be shifted horizontally on the machine frame 18 in order to adjust, for instance, the position of the rotation axis of the table 14 with respect to the axis of the worked globoid worm so that it will coincide with the axis of a worm wheel which is later to be set in engagement with this globoid worm.

The grinding machine is driven by a reversible driving mechanism 1 transmitting a rotating motion to a gear 2 which drives by way of a shaft 3 a worm gear consisting of a worm 4 and a worm wheel 5 connected to the rotating table 14.

The gear 2 is furthermore provided with another shaft 6 terminating in a transmission case 7, from which a chuck 19 projects, onto which the worked globoid worm 9 is clamped. The transmission case 7 contains a differential gear, enabling the turning of the worm wheel 5 by the feeding device 16 when the rotating table 14 is inits extreme position, that is if the stop 11 actuates the limit switch 13. The worked globoid worm 9 remains stationary during this feeding movement. After feeding is finished, that is after a time interval adjusted by a time switch 119 indicated in FIG. 5, the reversible driving mechanism is switched on and the rotating table 14 turns in direction of the arrow B into its starting position, where the stop 10 actuates the limit switch 12. The limit switch 12 changes the direction of movement of the reversible mechanism 1 and the rotating table 14 starts to move in direction of the arrow A.

The described cycle is repeated until the entire material allowance in a single tooth flank has been subsequently removed by grinding. The limit switch 12 thereafter cuts in the indexing device 8, causing it to turn the globoid worm 9 for an angle corresponding to the thread number of the globoid worm 9. This turning is accomplished solely in the starting position of the rotating table 14, that is where the stop 10 actuates the limit switch 12. The worm gear of the rotating table 14, that is the worm 4 and the worm wheel 5 are stationary during the course of indexing.

The preferred feeding device 16 is indicated in FIG. 3, 4 and 5.

It comprises a reversible regulating motor 101, preferably a hydraulic motor, a worm gear 102 is used to achieve the required ratio between the reversible motor 101 and a coupling shaft 112 which is driven by the worm gear 102. A coupling disk 103 for left hand feeding, a coupling disk 104 for right hand feeding and a worm 124 are supported by the coupling shaft 112. The worm 124 engages a worm wheel 106 driving an output shaft 113 which couples the fee-ding device 16 to the gear 2. The disks 103 and 104 are freely rotatable on shaft 112 and can be fixed with this shaft either individually, or both simultaneously by keeping means, for example by a magnetic clutch means 128,129. The coupling disks 103 and 104 are provided for left and right hand feeding respectively with a dog 120 and 121. In the rest or starting position prior to starting the feeding movement, both dogs 120 and 121 are urged by a common torsion spring 107 against a common stop 105, actuating thereby limit switches 108 and 111 respectively (see FIG. 4). Other limit switches 109 and 110 respectively are on the opposite side of the common stop for each of these coupling disks 103,104. The worm 124 is slidingly supported on the coupling shaft and its axial movement is determined by a stationary hydraulic cylinder 123, the piston rod of the piston 1 14 of which engages by means of a coupling 122 an extension of the worm 124, allowing a free rotating movement of the worm 124. Another extension 125 of the piston rod of piston 114 actuates in both extreme positions of the piston 114 limit switches 126 and 127 respectively.

As shown in FIG. 5, the direction of rotation of the reversible motor 101 is controlled by a reversing switch 115 and its speed by a regulating element, in the case given, a throttle valve 116. The reversing switch 115 is actuated by an adjustable time switch 119. The throttle valve 116 is controlled by means of a pickup 117 by a templet 118, fixed on the machine frame 18 of the grinding machine. The pick-up 117 is fixed on the sliding support of the rotatable table 14, so that it is actuated in the event the distance between the worked worm and the corresponding worm wheel is adjusted. The axis of the worm wheel is maintained coincident with the rotation axis of the rotatable table 14.

The described arrangement performs during the course of control of the feeding movement, i.e., when grinding tooth flanks of single or multithread worms, the following main tasks: 1. Removal of the grinding disk 15 from the ground flank of the tooth of the globoid worm 9 in the course of return into its initial position, that is in the course of its movement in direction of the arrow B.

The tooth flank of the globoid worm 9 is worked in the course of turning of the rotatable table 14 in direction A as indicated in FIG. 2. In the extreme position, that is after the limit switch 13 has been actuated by the stop 11, the reversible driving mechanism 1 is cut out. Simultaneously the piston 114 of the hydraulic cylinder 123 which has been up to now in its extreme right position, is shifted in direction C, so that the extension 125 actuates the limit switch 126, which cuts in the reversible driving mechanism 1 in the opposite direction and the rotatable table 14 turns without function in direction B into its starting position. By actuating the limit switch 12 by the stop 10 the reversible driving mechanism 1 is cut out and simultaneously the piston 114 of the hydraulic cylinder 123 is shifted in direction D into its right extreme position. The extension 125 actuates the limit switch 127, which cuts in the reversible driving mechanism and the rotatable table 14 starts to turn in direction A". This described cycle is repeated until the grinding is finished up to the preselected depth.

By shifting the piston 114 of the hydraulic cylinder 123 in linear direction C, the worm 124 of the worm gear 106 is shifted by an equal distance. By a subsequent turning of the worm wheel 106 and of the output shaft 113, the grinding disk 15 is removed from the tooth flank of the ground globoid worm 9 for a constant angular distance. By shifting the piston 114 in direction D the grinding disk 15 is approached to the tooth flank of the globoid worm 9 for an equal angular distance.

Continuous approaching and removal of the griding disk to and from the tooth flank of the worked globoid worm 9.

When adjusting the machine, the output shaft 113 of the feeding device 16 is turned by way of the gear 102 and the worm 124 with the worm wheel 106 by a continuous turning of the reversible regulating motor 101. By manual operation'of the reversing switch 115 it is possible to change the direction of rotation of the reversible regulating motor 101 and thus also the direction in which the rotatable table 14 with the grinding disk 15 is turned.

Feeding of the grinding disk 15 when grinding tooth flanks of a globoid worm in an automatic cycle. The feeding of the grinding disk 15 when grinding tooth flanks of globoid worms is accomplished by turning the rotatable table 14 with respect to a stationary globoid worm 9 for an angular distance, corresponding on the base circle of the globoid worm 9 to the required material allowance for grinding. From FIG. 13 it is obvious that for the same material allowance on the base circle of the globoid worm 9 having the distance a between the axis of the worm and the corresponding worm wheel and a globoid worm 9 having'the respective axial distance a, different values dub of angular deviations of the rotatable table 14 are required. The magnitude of feeding for one grinding operation, that is the magnitude of the material removal on the base circle of the ground globoid worm, is controlled by the time switch 119, in other words a certain material removal corresponds to a certain exact time of operation of the reversing switch 115 controlled by the time switch 119 and a certain time of rotation of the reversible regulating motor 101. The correction of the magnitude of the turning of the rotatable table 14, for instance if the axial distance of the worked worm and worm wheel is changed, is according to this invention accomplished by adjustment of the rotating speed of the reversible regulating motor 101. In the described example the throttle valve 116 is controlled by means of a pick-up 117 by a templet 118 fixed on the sliding support of the rotatable table 14. The pick-up 117 and the throttle valve 116 are arranged on the machine frame 18, so that even if the position of the rotatable table 14 on the machine frame 18 is changed, or if the axial distance between the worked worm and the corresponding worm wheel is changed, or the number of revolutions of the reversible regulating motor 101 is raised or reduced so that for the same time of operation of the re versible switch 115, the material removal measured on the base circle of the globoid worm 9 is always the same. It does not depend on the axial distance a between the worked globoid worm 9 and the respective globoid wheel.

FIG. 12 shows a threethreaded globoid worm. The individual teeth are marked X, Y, Z. The material allowance is indicated oneach tooth and the positions of the grinding disk at the start (1 and at the end (J of grinding are equally shown. In order to take away the entire material allowance, the rotatable table 14 must be turned with respect to a stationary globoid worm 9 for the angle 4),, 4),, 4a,. The feeding device according to this invention secures a turning of the rotatable table 14 with respect to a stationary globoid worm 9 for the required angle. After removal of the entire material allowance for grinding, that is after turning of the rotatable table 14 with respect to the stationary globoid worm 9 for the angle 11;, in direction A (the grinding disk in position J the rotatable table 14 with the grinding disk 15 is turned continuously for the same angle in direction B. The grinding disk 15 takes position 1,.

After the performed indexing, that is after the turning of the globoid worm 9 for an angular distance corresponding to the respective distance of the teeth, the grinding disk 14 is in position 1,, with respect to the globoid worm 9. This described cycle is repeated as often as the number of threads contained on the worked glo boid worm 9. The entire cycle is finished as soon as the grinding disk 15 reaches position 1,. The mechanical storage device of the feeding device according to this invention insures, that the angular distances 45,, 4a, of the turning of the rotatable table 14 are equal.

The operation of the mechanical storage device will be now described with reference to the diagrams in FIG. 6 to 11 where the positions of both coupling disks 103 and 104 are shown side by side rather than axially, only for convenience of understanding.

In the starting position (FIG. 6) the coupling disks I03 and 104 (see also FIG. 3) are freely rotatable on the coupling shaft 112 and their dogs 120 and 121 are urged by the torsion spring 107 towards the stationary stop 105. The dog 120 actuates the limit switch 108, the dog 121 the limit switch 111.

By manual operation of the feeding device (FIG. 7) the coupling disk 103 for left hand feeding is coupled by actuating the magnetic clutch element 128. The time switch 119 is adjusted to a chosen time, corresponding to the material removal in the course of one partial grinding cycle and acts to close for this time period the reversing switch 115. The reversible regulating motor 101 is during this time activated. The coupling disk 103 for left hand feeding turns for the angle 4:, (see FIG. 7, left part) removing dog 120 from notch 108. The coupling disk 104 remains freely rotatable on the shaft 112 and the dog 121 remains in contact with the stop 105, actuating the limit switch 111. Thus the material removal for one partial working cycle has been preselected.

The material is now subsequently removed by grind ing, whereby at each partial cycle the same depth of material is removed, until the dog 120 reaches a position indicated in FIG. 8 by the angular displacement d; with respect to the starting position, whereby n d), where n is the number of partial cycles required for removal of the entire material allowance. At this time the operation of the feeding device is manually interrupted. The grinding disk 15 is in position J (FIG. 12). Simultaneously the coupling disk 104 for right hand feeding is coupled with the coupling shaft 112 by means of the magnetic coupling means 129. The relative angular position of dogs 120 and 121 of the coupling disks 103 and 104 the mechanical storage device is determined by the angle corresponding to the turning of the rotatable table 14 for the angle The actual distance of both dogs 120, 121 corresponds to the angle 115, which remains constant in the course of the further working of the globoid worm 9. This angle d) is indicated in the right part of FIG. 8 between the position 120' of the dog 120 of the coupling disk 103 shown in broken lines and the dog 121. The dog 121 has up to now remained in its starting position.

Simultaneously with the interruption of feeding and coupling of the coupling disk 104 for right hand feeding with the coupling shaft 1 12, the reversing switch 115 is closed. The reversible regulating motor 101 starts to rotate in the opposite direction. Both dogs and 121 start to move in the opposite direction E. In FIG. 9 an intermediate position of both coupling disks 103 and 104 with their dogs 120 and 121 is shown in the course of their return movement. Both dogs 120 and 121 have turned for an angle p. Their relative position is determined by the angle lll. In the left part of FIG. 9 is indicated the angular track of dog 120 from its original position 120 shown in broken lines to the actual position 120. In the right part of FIG. 9 the actual position of dog 121 is shown and the position 120" of dog 120 which is part of the coupling disk 103, indicating their mutual angular displacement 111.

The return movement of the reversible regulating motor 101 together with the coupling shaft 112 and coupling disks 103 and 1041 continues until dog 120 hits the stop 105 closing the limit switch 108 (see FIG. 10). Dog 121 has been turned from its original position for the angle The limit switch 108 simultaneously generates an impulse for indexing by the indexing device 0 to turn the globoid worm 9 for an angle corresponding to one tooth distance while the rotatable table 14 and the disk 15 remain stationary. The left part of FIG. 10

shows at 120' the original position of dog 120 in broken lines, the right part of FIG. 10 at 121' the original position of dog 121. Both coupling disk 103 and 104 have remained coupled with shaft 112 and have simultaneously turned for the angle 4) in the direction indicated in FIG. 10.

After finishedindexing the whole cycle is repeated. The dog 120 turns from its starting position where the limit switch 108 is closed, again for the angle 4), in direction F. The dog 121 turns equally for the angle as shown in FIG. 11. This value has been preselected manually prior to starting the first partial working cycle and the whole operation as described for the first thread is repeated for the following threads, whereby these following working cycles are terminated by closing the limit switch 111 by the dog 121 of the coupling disk 104.

After the grinding of all teeth of the worked globoid worm 9 is finished, the entire arrangement comes to a stop. By manual operation by preselection of a new working cycle, both coupling disks 103, 104 are released and the torsion spring 107 returns both dogs 120, 121 into their starting position, where dog 120 closes the limit switch 108 and dog 121 the limit switch 1 1 1. The feeding device is thus prepared for further action, the prior preselected angle of the mechanical storage device is annuled.

I claim:

1. Feeding device for machine tools, particularly for the grinding machines of globoid worms having reversible drive means for the tool and workpiece respectively, said device comprising in combination:

a coupling shaft,

a second reversible driving means driving said coupling shaft,

a coupling member for left hand feeding anda coupling member for right hand feeding rotatably supported on said coupling shaft,

dog means on each of said coupling members,

a stationary stop,

spring means urging said dog means of both coupling parts against said stationary stop,

limit switches controlling individual phases of the machining operation actuated by said dog means in their extreme positions,

means for coupling said coupling members with the coupling shaft both individually, and jointly, and

an output shaft connected to the reversible driving means of the tool and workpiece respectively.

2. The feeding device according to claim 1 including gear means interposed between the coupling shaft and the output shaft of the mechanical storage device, means for creating in said gear means a clearance at the start of the reverse movement of reversible driving means and for eliminating this clearance after start of the forward movement.

3. The feeding device according to claim 1 including an adjustable time switch controlling the time of operation of the reversible regulating driving means of the storage device.

4. The feeding device according to claim 1 including regulating means adjusting the speed of the regulating driving means of the mechanical storage device in dependence on changing working parameters. 

1. Feeding device for machine tools, particularly for the grinding machines of globoid worms having reversible drive means for the tool and workpiece respectively, said device comprising in combination: a coupling shaft, a second reversible driving means driving said coupling shaft, a coupling member for left hand feeding and a coupling member for right hand feeding rotatably supported on said coupling shaft, dog means on each of said coupling members, a stationary stop, spring means urging said dog means of both coupling parts against said stationary stop, limit switches controlling individual phases of the machining operation actuated by said dog means in their extreme positions, means for coupling said couplinG members with the coupling shaft both individually, and jointly, and an output shaft connected to the reversible driving means of the tool and workpiece respectively.
 2. The feeding device according to claim 1 including gear means interposed between the coupling shaft and the output shaft of the mechanical storage device, means for creating in said gear means a clearance at the start of the reverse movement of reversible driving means and for eliminating this clearance after start of the forward movement.
 3. The feeding device according to claim 1 including an adjustable time switch controlling the time of operation of the reversible regulating driving means of the storage device.
 4. The feeding device according to claim 1 including regulating means adjusting the speed of the regulating driving means of the mechanical storage device in dependence on changing working parameters. 